January/February 2023 - 96

landfill but can enhance concrete's
per formance depending on the
application. For every portion of
portland cement replaced by SCMs
there is an improvement in the
environmental footprint of concrete,
including a reduction in GHGs and air
pollutants. Combined with the fact that
using these SCMs reduces waste, their
use overall contributes to enhanced
sustainability in the construction
industry. A study by the National Ready
Mixed Concrete Association shows that
significant global warming potential
reduction is obtained by simply
substituting a portion of the cement in
an OPC mix with various amounts of
SCMs. It is important to note that up to
an additional 10% reduction in CO2 can
be achieved by simply substituting the
OPC in these mixtures with PLC.
Recycled Materials: In addition to
SCMs, increasing the use of other
recycled materials is another sustainable
option available to specifiers.
One well-documented use of recycled
materials involves the crushing and
sizing of old concrete elements (from
construction and demolition waste) into
new construction aggregates. These
recycled concrete aggregates, or RCAs,
can be used in concrete mixes for many
geotechnical applications including
foundations. Other materials that are
gaining increased attention by researchers
and practitioners for use in concrete
mixes include steel slags, recycled glass
and plastics, scrap tires, hemp fibers,
rubber, and numerous others.
Design Optimization: Optimization
during the design phase of a project
takes a whole life design perspective
that involves both an integrated
design approach and an integrated
team process. A rational approach is
encouraged to eliminate unnecessary
and costly overdesign and to keep
codes and standards updated with
actual structural performance, as well
as the latest developments in research.
Every foundation is designed on
basic principles including strength,
stiffness, stability, durability and
long-term performance. Foundation
systems can also be optimized by
considering the size, shape and
spacing of structural components
including how and where those
components are connected to most
efficiently transfer loads. One common
example is the use of higher
strength concretes to decrease the
overall volume of concrete needed.
While the higher strength concrete
often requires higher cement contents,
the overall structural system can be
designed with a lower carbon footprint
because the overall system has
been optimized.
Performance-Based
Specifications
Civil and geotechnical engineers are
strongly encouraged to shift from
prescriptive specifications and move
toward performance specifications.
Prescriptive specifications are like a
recipe with ingredients listed while
performance specifications focus on the
end results. Performance specifications
empower the material producer and
contractor with the flexibility needed to
innovate and leverage the latest technology
to improve structural perforCivil
and geotechnical
engineers are strongly
encouraged to shift from
prescriptive specifications
and move toward performance
specifications.
mance, energy efficiency, resiliency and
carbon sequestration. Performance
specifications also allow concrete
producers to design with the application
in mind rather than use the same
specifications regardless of the project.
Conclusion
The opportunity for the deep foundations
community, including project
owners, general and specialty contractors,
engineers, manufacturers,
suppliers, educators, and students, to
positively impact the carbon footprint
of projects is clear. It must be kept in
mind that alternatives that provide the
lowest initial carbon footprint during
construction do not always provide the
lowest overall carbon footprint over the
full life of the structure, and tools such
as LCA must be leveraged to accurately
evaluate the environmental impacts.
The ultimate success of carbon neutrality
for the cement and concrete
industry depends on the collaboration
of all stakeholders throughout the value
chain. With the impending climate
crisis, societal momentum and the
commitment of the entire cement and
concrete industry will lead to carbon
neutrality throughout the entire value
chain by 2050, and future generations
will reap the benefits of the commitments
and actions taken today.
Greg Halsted, P.E., is the manager of
pavements and geotechnical support for the
Portland Cement Association. He has more
than 25 years of experience using cement in
the pavements, geotechnical and concrete
industries.
Joshua Gilman, P.E., is the manager of
water resources and geotechnical support for
the Portland Cement Association. He has
more than 10 years of experience in these
markets, with a focus on dam engineering
and dam safety.
96 * DEEP FOUNDATIONS * JAN/FEB 2023
January/February 2023

Table of Contents for the Digital Edition of January/February 2023
